That seems pretty cut & dry. I've confirmed with the exchange that this number represents QHPs only; it doesn't include SHOP (small business) or standalone Dental plans.

Last year Colorado ended up with 140,327 QHP selections during open enrollment out of 11,688,074 total...or about 1.2% of the national total.

A straight extrapolation of 6,718 QHPs through Sunday would be around 560,000 QHP selections to date, which would be around 28% lower than the 780K through Sunday which I've estimated. Again, however, there's still way too little hard data to come to any conclusions yet.